Safety cut-out for electrical apparatus



N M 1 1.) LEMP & M. J. WIGHTMAN..

SAFETY OUT-OUT FOR ELEOTRIGAL APPARATUS.

No. 517,120. Patented Mar. 27, 1894.

INVENTOR8 BY y 2/- www- Al TORIAEY lyrFLkun /////////////////l/ i 5 x m!mmomu. umosnAPmma cuunr'rn wasumwrou. n. c.

UNITED STATES PATENT OEEIcE.

HERMANN LEMP AND MERLE J. WIGHTMAN, OF HARTFORD, CONNECTICUT, ASSIGNORSTO THE SCHUYLER ELECTRIC COMPANY, OF CONNECTICUT.

SAFETY OUT-OUT FOR ELECTRICAL APPARATUS.

SPECIFICATION forming part of Letters Patent No. 517,120, dated March27, 1894.

Application filed July 31, 1886. Serial No. 209.656- (No model.)

To aZZ whom it may concern.-

Be it known that we, HERMANN LEMP and MERLE J. WIGHTMAN, citizens of theUnited States, and residents of Hartford, in the county of Hartford andState of Connecticut, have invented certain new and useful Safety Cut-Outs for Electrical Apparatus, of which the following is aspecification.

Our invention relates to safety cut outs for IC electrical apparatus andis designed to provide a novel means whereby a short or safety path orbranch circuit may be formed around an apparatus in case of rupture ofthe circuit in such apparatus, orin case of the flow upon :5 suchcircuit of an abnormally high current calculated to endanger the safetyof said device. Y

Our invention is applicable to electric lamps generally but is moreespecially designed for that type of lamp ordinarily termed anincandescent lamp.

The invention consists especially in interposing, between the twoelectrodes of the circuit through which a path is to be established 2 5on the occurrence of abnormal conditions, a

material which is normally an insulator but which, when exposed to heat,developed either by the so called electric are or by a high potentialcurrent of any kind sufficient in potential to force its way over thespace bridged by the said material, will be reduced to a metallic orconducting state thus forming a di- Eect or short circuit over whichcurrent may Our invention consists further in the combination with anelectric lamp, of a mass of material that is normally an insulator butbecomes a conductor by the action of heat, interposed between the twoelectrodes of the lamp so as to normally insulate the same from oneanother, but on a breakage of circuit in the lamp to fuse and be therebyreduced to such a condition as to become a conducting path around thesame.

5 Our invention consists also in the combination with the enteringconductors or electrodes for an incandescent lamp, of an interposed massof material consisting of a substance that is normally an insulator butwhich, when exposed to very intense heat either by an electric are or ahigh potential current, becomes reduced to ametallic state thus becominga conductor and short circuiting the current around the lamp.

As a material suitable for the purpose of 5 our invention We havediscovered that We may employ a compound of metal oxides or salts andborax, carbonate of soda, or any other salt which facilitates fusion. Wehave obtained good results from the employment of peroxide of lead andborax, and lead and borax, oxide of copper and silicate of soda, andchlor ammoniate of platinum. These substances can be mixed together andapplied in the form of a paste. Under some circumstances they may at thesame time serve as a cementing material as will be hereinafterdescribed.

In the accompanying drawings: Figure 1, is a diagram illustrating ourinvention, and the manner of applying the short circuiting material.Fig. 2, is a side elevation of the parts of an incandescent lamp towhich our invention is applied. Fig. 3, is a cross section on the lineY, Y, of Fig. 2. Fig. 4, illustrates another way of applying thematerial to the entering conductors or electrodes of an incandescentlamp. Fig. 5, is a cross section on the line X, X, of Fig. 4. Fig. 6, isa vertical section of the base of an electric incandescent lamp showingthe manner in which the short circuiting material may be employed as thecementing material to hold the conductors leading to the lamp in place.

Referring to Fig. 1, L, indicates the con- 85 doctor or circuit overwhich current flows from any source to a working resistance R,consisting of the filament of an incandescent lamp, the carbon of anelectric arc lamp, or any other apparatus. A, B, indicate poro tions ofthe conductor or circuit forming respectively positive and negativepoles and brought into any desired proximity suitable for the practiceof the invention. The poles A, B, are preferably located near the work-5 ing resistance R, but might be at any desired distance from the same.Interposed between the poles A, B, is a mass of material indicated at M,which is normally an insulator, or is sufficientlyinsulatingin itsquality too to prevent the current from passing in short circuit from Ato B, and to therefore cause the current to flow in the normal way solong as there is circuit for it through the working resistance R. Onrupture of circuit however through the working resistance R, the currentforces its way across the space between the electrodes A, B, and in sodoing fuses or reduces the material so as to reduce it to a metallicstate, thus makinga conductor of it. The current which fuses suchmaterial might be an electric arc current in some cases, as for instancein the case of an incandescentlamp where the electrodes A, B, mayconsist of the entering conductors of the lamp and may be arranged insuch proximity that the electric are traveling down the conductors onrupture of the filaments will finally strike the mass of material M, andreduce it to a metallic state.

In Fig. 2, the entering conductors of an incandescent lamp are indicatedat H, H. The two poles of the circuit are formed of two strips ofpliable conducting materialD, D, one of which is wrapped around and isin contact with one of the entering conductors ll, while the other iswrapped around and is in contact with the other entering conductor. Eachstrip D, is carried around the opposite conductor H, but is normallyinsulated therefrom and from the other strip D, by an interposed mass ofthe copper compound before specified, or of other materials adapted tooperate in the same way. On rupture of the filament of the lamp theelectric are passing downward finally envelops the conductors or polesD, and the interposed mass of material, thus fusing the latter andforming the short circuit as before described.

In Fig. 4, the conductors H, are brought sufficiently near together toconstitute the poles A, B, across which the current may force its way,or between which an electric arc may exist including or passing over themass of normally insulated compound. The compound is indicated at M, asbefore, and is enveloped in a wrapping of asbestus or other material.

The two conductors of the lamp forming the poles A, B, of Fig. 5,consist of sheet metal brought into close proximity as indicated.

In Fig. (3, the entering conductors of the lamp are connected to supplyconductors in the hollow neck of the lamp globe, and the supplyconductors with the strips G, G, conveying current thereto, are anchoredin the mass of the compound. The strips G, G, which consist of flatplates of metal adapted to be slipped into a spring switch of the kinddescribed in another application filed by us are separated normally fromone another by the compound. In case of rupture of the filament of thelamp, the high potential current of the circuit on which the lamp isemployed will force its way across the interval between the conductorsor poles of the circuit and through or over the compound thus reducingthe same to a metallic or conducting state.

The invention is better adapted to application to incandescent lampsdesigned for employment on electric arc or high potential circuits, thantoincandescent lamps supplied in multiple are from low tension circuits.

It will be obvious that the principle of our invention is not confinedin its applications and that it is adaptable to any kind of electricalapparatus where it is desirable to form a short circuit or safetycircuit in case of rupture of the current through the apparatus itself,or in case of the access to the circuit of an abnormally high currenttension from the same source or from another source, and sufficient inamount to endanger the devices in the normal circuit.

o do not claim broadly the interposition between two poles of a circuitof a substance of such composition that itis normally aninsulatorbutwhich on an extra stress of current simplyfurnishes atemporary bridge for such current for the purpose of establishing an arebetween said poles and which is then immediately fused or volatilizedleaving the formation of a permanent bridge dependent upon the fusion ofsaid poles.

\Vhat we claim as our invention is- 1. In a safety cut-out, thecombination with two poles of thecircuit, of an interposed mass ofmaterial consisting of a substance which is normally an insulator butwhich, by heat, produced by a current passing thercover is reduced toametallic or conducting state and formsa permanent bridge between saidpoles, as and for the purpose described.

2. In an incandescent electric lamp, entering conductors connected withor themselves forming poles of the circuit that are in close proximityin combination with a separating mass of material which is normally aninsulator but which fuses under the action of an electric current andbecomes decomposed to such an extent as to form a permanent cutoutbetween the lamp conductors.

3. In a safety or shunt cutout device for electric apparatus, thecombination with the two poles or conductors A, 13, arranged inproximity to one another, of an interposed compound forming normally aninsulatorbut adapted to be fused under the action of the electriccurrent passing from one electrode to the other, and thereby decomposedto such an extent as to form a conducting bridge be tween the lampconductors, as and for the purpose described.

Signed at Hartford, in the county of Hartford and State of Connecticut,this 1st day of July, A. D. 1880.

HERMANN LEMP. MERLE J. WIGHTMAN.

Witnesses:

()LOF OFFREN, Oscan URBAN.

